Update CHANGELOG.md

Co-authored-by: Andrew Ross <[email protected]>
Signed-off-by: Lukáš Vlček <[email protected]>

Author: lukas-vlcek

CHANGELOG.md

@@ -18,6 +18,6 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 
 ### Changed
 
-- Lower down the log level to DEBUG ([#18186](https://github.com/opensearch-project/OpenSearch/pull/18186))
+- Change single shard assignment log message from warn to debug ([#18186](https://github.com/opensearch-project/OpenSearch/pull/18186))
 
 [Unreleased 2.19.x]: https://github.com/opensearch-project/OpenSearch/compare/fd9a9d90df25bea1af2c6a85039692e815b894f5...2.19